Electronic control circuit for a dryer with timer runout



Oct. 14, 1969 A. J. ELDERS 3,471,938

ELECTRONIC CONTROL CIRCUIT FOR A DRYER WITH TIMER RUNOUT 771145? More@ ADM/V653 CAA/.5 7a "oFF" Pos/r/o/V EN@ efve a iw ATTORNEYS oct. 14, 1969 A. J. eLm-:Rs 3,471,938

ELECTRONIC CONTROL CIRCUIT FOR A DRYER WITH TIMER RUNOUT Filed Orb. L, 1967 4 Sheets-Sheet 2 l l r -1- 1 q 7; 77 754;/ EDN OF/ 7 l l I7@ 76M l 1 l i LZ2 l/ 7:5 -o/-a ..7 -o/c f5 i jp BY Y ATTORNEYS Oct. 14, 1969 A. J. ELDERS 3,471,938

ELECTRONIC CONTROL CIRCUIT FOR A DRYER WITH TIMER RUNOUT IBI/@9&0 J ATTORNEYS Oct. 14, 1969 l A, J, ELDERS 3,471,938

ELECTRONIC CONTROL CIRCUIT FOR A DRYER WITH TIMER RUNOUT Filed Oct. 4., 1967 4 Sheets-Sheet 4 Z: E .4 Q .oo o I O/OZ/Ff Ec', '[67 7a 2:.: 57- I v l 1 o 64 l o c /03 5 5C@ /M w i l l 1 \'vE/\1'T0R.

3,471,938 ELECTRONIC CONTROL CIRCUIT FOR A DRYER WITH TIMER RUNOUT Alvin I. Elders, Lincoln Township, Mich., assignor to Whirlpool Corporation, Benton Harbor, Mich., a corporation of Delaware Filed Oct. 4, 1967, Ser. No. 672,833 Int. Cl. F261) 25/22; G0511) 11/28 ILS. Cl. 34-45 8 Claims ABSTRACT OF THE DISCLOSURE A control system for an appliance such as a clothes dyer wherein clothes are placed in a clothes receptacle and dried to a predetermined condition of dryness. The control system includes an electronic control circuit which generates a control signal in response to sensing a predetermined condition of the clothes being dried. A timer motor is connected to the control circuit for operation therefrom. The timer motor is of the type which requires full-wave alternating current to be applied thereto for peration thereof. Therefore, application of half-wave pulses to the timer motor will maintain the motor in the inoperative condition. During periods of operation of the appliance prior to sensing the predetermined condition of the clothes half-Wave pulses are applied to the timer motor by the control circuit. However, upon sensing of the predetermined condition the electronic control circuit applies full-wave alternating current to the timer motor thereby rendering the timer motor operative. The timer motor is used to control auxiliary functions of the appliance such as the cool down cycle and/or the antiwrinkle cycle of a clothes dryer, while the drying cycle of the clothes dryer is controlled completely by the electronic control circuit. The control system includes a tWist-to-start control knob which is used to initiate the operation of the appliance.

BACKGROUND OF THE INVENTION Field of the invention This invention relates generally to a control system for appliances and more particularly to a control system for a clothes dryer wherein sensing elements are placed within the clothes receptacle of the dryer to sense the relative condition of dryness of the clothes. Specifically, the present invention is directed to the use of electronic control circuit in combination with a timer motor such that the electronc control circuit has complete control of the drying cycle of the dryer and after the desired dryness of the clothes is reached a control signal Will initiate the operation of the timer motor to control auxiliary functions of the dryer such as the cool down and/ or antiwrinkle cycle.

Description of the prior art Heretofore, control systems for appliances such as clothes dryers incorporated electronic control circuits which would sense the relative dryness of the clothes within a predetermined range of dryness after which time a control signal would be generated to initiate the operation of a timer. The timer would then terminate the drying cycle after a preselected period of time set into the timer has been runout. This type of control system has a disadvantage in that each time the operator of the dryer would start the operation of the dryer the timer would have to be set to some predetermined period of time depending on the condition of dryness desired. This required nited States Patent O Fice the operator to remember the previous timer setting which produced the desired dryness of clothes and correlate it with the size of clothes load being dried since in a strictly timer controlled dryer the duration of the drying cycle is not dependent on the dryness of the clothes but only on the time as preset on the timer.

Another disadvantage of control systems of the prior art is that of the method of switching used to initiate the operation of the appliance. That is, control systems using variable runout timers as mentioned above usually employ push-to-start switches which are depressed after the desired period of time has been selected on the timer dial. Such push-to-start switches can be accidentally actuated by bumping the switch with an object or by small children.

SUMMARY OF THE INVENTION According to this invention, there is provided a control system for a clothes dryer wherein sensing elements are placed within the clothes receptacle of the dryer to sense the relative dryness of the clothes. Specifically, the present invention is directed to the use of an electronic control circuit in combination with a timer such that the electronic control circut has complete control of the drying cycle of the dryer and after the desired dryness of the clothes is reached a control signal will initiate the operation of the timer to control auxiliary functions of the dryer such as the cool down and/ or antiwrinkle cycle.

Accordingly, it is an object of the present invention to provide a control system wherein the drying cycle of a colthes dryer is controlled completely by an electronic circuit and wherein auxiliary functions of the dryer are controlled by a timer having a fixed preset time interval.

Another object of the present invention is to provide a control system for a clothes dryer wherein the timer is actuated by a twist-to-start selector knob which initiates the operation of the dryer and presets the timer for a fixed duration of runout after it is made operative by the electronic current.

Another object of the present invention is to provide a control system for an appliance which includes an electronic control circuit to control the operation of a timer motor by applying half-wave pulses of alternating current to the timer motor during periods when the timer motor is to be inoperative, and by applying full-wave alternating current to the timer motor during periods when the timer motor is to be operative.

Another object of the present invention is to provide a control system for an appliance which includes a new and novel control circuit having a minimum number of components and relatively simple circuitry and which will function properly to control the operation of the appliance.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE l is an elevational functional view of the control panel of the dryer showing the disposition of the control knobs thereon used to initiate various modes of operation of the dryer;

FIGURE 2 is a schematic wiring diagram showing one form of the circiut arrangement of the control system of the present invention;

FIGURE 3 is a schematic diagram showing an alternate arrangement of an electronic control circuit which can be used in the control system of FIGURE 2;

FIGURE 4 is a schematic wiring diagram illustrating another alternate arrangement of an electronic control 3 circuit which can be used in the control system of FIG- URE 2;

FIGURE 5 is a schematic wiring diagram showing another control system which can incorporate the electronic control circuits shown in FIGURES 2, 3, and 4; and

FIGURE 6 is a timer sequence chart showing the operative condition of various timer controlled switches ernployed with the control system of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the principles of the present invention are of utility When used in combination with any dryer construction, a particularly useful application is made to dryers for fabrics and the like, an illustrative embodiment of which is described in U.S. Patent No. 3,409,997, issued Nov. 12, 1968, and assigned by the applicants, Clifton A. Cobb and Gordon J. Krolzick, to Whirlpool Corporation, assignee of the present invention.

Throughout the description of the preferred embodiments of the present invention it will be understood that like reference numerals throughout the various views of the drawings are intended to designate similar elements or components.

Seen in FIGURE 1 is a control panel 60 which may be used to program the cycle of operation for a clothes dryer embodying the control of the instant invention. The control panel 60 includes an air-heat slide switch 61 which allows the operator to select either normal heated air ow through the dryer or air ow without heat. An antiwrinkle selector knob 62 is provided on the control panel 60 to allow the operator to optionally select the antiwrinkle operation of the dryer which will then follow after the normal drying cycle has terminated. (See U.S. Patent No. 3,398,461, issued Aug. 27, 1968, assigned to Whirlpool Corporation, for a description of the antiwrinkle cycle referred to here.) The control panel 60 includes a dryness control knob 63 which includes successive numerical indicia thereon to indicate the relative selected dryness to which the clothes will be dried. A novel feature of the control panel 60 is the twist-to-start knob 64 which, in turn, is ganged to a timer that is utilized only to control various auxiliary functions of the dryer.

It will be appreciated that the timer operated by twistto-start knob 64 has one preset cycle which is not utilized to control any portion of the drying operation of the dryer. Therefore, once the dryness control knob 63 is set to the desired position, it need not be changed each time the dryer is placed in operation. That is, the operator may select the desired dryness of clothes for a plurality of loads and by merely turning the twist-to-start knob 64, each load of clothes will be dried to the same relative dryness regardless of load size or clothes type.

Referring now to the timer sequence chart of FIGURE 6, the operation of the timer actuated by tWist-to-start timer knob 64 will be described. The timer sequentially controls closure of live switches generally indicated T1, T2, T2, T4, and T5. When timer knob 64 (refer to FIG- URE 1) is in the off position, no timer switches are closed and the timer is in the band indicated 64a. Upon twisting timer knob 64 counterclockwise 65 degrees from the olf band to the run band as indicated by arrow 64b, timer switches T1, T2, and T2 will progressively close. When timer knob 64 has been rotated 65 degrees from the oi position, a spring (not shown) within the timer will be engaged whichrressts further counterclockwise rotation of timer knob 64. Thus, in order to close timer switches T4 and T5, timer knob 64 must be rotated against the resisting torque generated by the spring. Upon rotation of timer knob 64 into the start band, which is 90 from the off band, timer switches T4 and T5 will close. When timer knob 64 is released, the spring will rotate timer knob 64 back into the run band as indicated by arrow 64C. This will open switches T1 and T5 while switches T1, T2 and T3 remain closed. The timer remains in the run band until an electronic control initiates '4 a timer motor whereupon the timer switches T3, T2'and T1 will be progressively opened as indicated by arrow 64d.

For a better understanding of the cooperation of the various control knobs of the control panel 60 with the control system of the dryer, reference is now made to FIGURE 2. FIGURE 2 shows a control system 66 which includes an electronic control circuit 67 the sole function of which is to control the drying portion of the drying cycle of a clothes dryer. The control system 66 is connected to a source of alternating current through a pair of lines L1 and L2 in the conventional manner.

A door switch 70 has the normally closed contact NC thereof connected to the line I,2 and the movable contactor thereof connected to one terminal of the pulser motor 71. Pulser motor 71 operates a cam (not shown) which closes a pulser switch 86 for 5 seconds during each 5 minutes of run time of motor 71 to effect the anti- Wrinkle cycle. The other terminal of the pulser motor 71 is connected to a movable contactor 72 of an antiwrinkle switch 73. The antiwrinkle switch 73 is controlled by the selector knob 62 shown in FIGURE l. The movable contactor 72 is shown in engagement with a stationary contact 72a which, in turn, is connected to line L1 through a normally open relay contactor 74 and a timer switch T1. Also associated with the antiwrinkle switch 73 is a second movable contactor 76 which alternately eugages stationary contacts 76a and 76b. The stationary contact 76a is connected to stationary contact 72a, and the movable contactor 76 is connected to an input terminal EC1 of the electronic control circuit 67 through a line 77. When the antiwrinkle selector knob is in the on position, the contactors 72 and 76 are positioned as shown.

yConnected in parallel with the pulser motor 71 is a relay coil 78 which, in turn, is connected to the line L1 through a timer switch T5 and a line 79. Relay coil 78 when energized operates relay contactor 74. The timer switch T5 is a momentary switch which remains closed only as long as the twist-to-start selector knob 64 is held in the start position.

A drive motor -80 includes a start winding 81 and a run winding 82 which are connected in parallel through a centrifugal switch 83. One terminal of the motor 80 is connected to the line L2 through the door switch 70 while the other terminal of the motor 80 is connected to the line L1 through the timer switch T4 as long as the twistto-start selector knob `64 is held turned to the start position. It is also connected to the line L1 through a line 87 and pulser contactor 86 which is actuated by the pulser motor 71. When the drive motor 80 is energized the centrifugal switch 83 disengages the start winding 81 and engages a stationary contact 83a which, in turn, is connected to a timer switch T2.

According to the present invention, the drying portion of the various cycles of operation of the dryer is completely electronically controlled by the electronic control circuit 67. The terminal EC1 of the electronic control circuit 67 is connected to movable contactor 76 through line 77. The terminal EC2 is connected to one terminal of the pulser switch 86 and the stationary contact 76b of the antiwrinkle switch 73. The terminal EC3 is connected to terminal EC2 through a relay contactor 89, which, by way of example, may be a reed switch. Also connected to the terminal EC5 is one terminal of a timer motor 90 which, in turn, has the other terminal thereof connected to the line L2 through the door switch 70. The timer motor operates cams (not shown) which sequently control actuation of timer switches T1, T2 and T3. Timer switches T4 and T5, which are momentarily actuated switches, are closed by turning twist-tostart knob 64 to the start position.

The contactor 89 is actuated by a relay coil 89a which is energized by the electronic control circuit 67 in response to sensing the desired preset condition of dryness of the clothes within the dryer.

A heat source 91 has one terminal thereof connected to the line L1 through the timer switch T3 and the other terminal thereof connected to the line L2 through the door switch 70, a motor operated centrifugal switch 93, and an air-heat switch 92. The air-heat switch 92 is actuated by the selector level 61 of the control panel 60, shown in FIGURE 1. Therefore, when the air-heat selector 61 is in the air position, the switch 92 is open thereby preventing energization of the heat source 91.

In order to sense the relative dryness of clothes within the dryer, a sensor assembly 54 is provided. Sensor assembly 54 comprises two electrically isolated electrodes positioned within the treatment chamber of a clothes dryer as described in U.S. Patent No. 3,391,468, issued July 9, 1968, and assigned by the applicant, Douglas I. Walker, to Whirlpool Corporation, assignee of the present invention. The electrodes function to monitor the moisture present in the clothing as it falls against them, thereby bridging the gap from one electrode to the other. If clothing is relatively damp, a low resistance will be sensed between the electrodes, whereas dry clothing will effect a high resistance electrical bridge.

The sensor 54 has one electrode thereof connected to ground potential and the other terminal thereof connected to a terminal ECG through a resistor 96 and a switch 92a. The switch 92a is ganged together with the switch 92 and is controlled by the air-heat selector 61, of FIGURE l. The terminal ECG is selectively connected to a terminal EC5 through a switch 92b which is also ganged together with the switch 92 and controlled by the air-heat selector 61. With air-heat selector 61 turned to heat, switches 92, 92a and '92b are all closed as shown in FIGURE 2. A terminal EC4 of the electronic control circuit 67 is connected to the line L2 thereby completing the circuit for the electronic control circuit 67.

The electronic control circuit 67 includes a diode 97 which is connected in series with a resistor 98 and a potentiometer 99 to form a charging circuit for a capacitor 100. The charge rate of the capacitor 100 is selected by varying the position of the wiper arm of the potentiometer 99 which corresponds to changing the relative position of the dryness control knob 63, of FIGURE 3. The wiper arm of the potentiometer 99 is connected to terminal ECG through a line 101 while the circuit point 102, between the potentiometer '99 and the capacitor 100, is connected to terminal EC5 through a line 103. The other terminal of the capacitor 100 is connected to terminal EC4 through a line 104.

A second diode 106 is connected in series with a resistor 107 which, in turn, is connected to a parallel connected capacitor 108 and resistor 109 which form a filter. The DC potential developed across capacitor 108 is applied to a line 110. A diode 111 is connected between circuit point 102 and line 110. The diode 111 operates to discharge the capacitor 100 and the neon lamp 117 whenever silicon controlled rectifier 116 is rendered conductive by providing a current path through the diode 111 and the silicon controlled rectifier 116. Also, the line 110 is connected to a resistor 113.

A resistor 114 is connected between line 104 and the gate electrode of a silicon controlled rectifier 116, and also a neon lamp 117. When the charge on capacitor 100 reaches the ionization Voltage of neon lamp 117, lamp 117 fires and delivers a current pulse through a current limiting resistor 112 to resistor 114 which, in turn, applies a forward bias between the gate and cathode electrodes of the silicon controlled rectifier 116 to cause conduction thereof.

The anode of the silicon controlled rectifier 116 is connected to relay coil 89a which, in turn, is connected between the junction of resistor 113 and a resistor 118 which form a voltage divider network. Upon rendering the silicon controlled rectifier 116 conductive, the coil 89a becomes energized to actuate contactor 89.

For a better understanding of the operation of the control system 66 of FIGURE 2 it is necessary to evaluate the respective selected cycles of operation. By way of eX- ample, it will first be assumed that the air-heat selector 61 is in the heat position and that the antiwrinkle knob 62 is in the off position. This condition will cause the movable contactors 72 and 76 of the antiwrinkle switch 73 to be in the open condition, opposite to that shown on the drawing. Additionally, setting air heat selector 61 to heat will close switches 92, 92a and 92h as shown on the drawlng.

To start the operation of the dryer the operator will merely turn the twist-to-start knob 64 from the off position to the start position. As heretofore explained, when knob 64 is turned toward the start position, timer switches T1, T2 and T3 are progressively closed. Upon urging knob 64 into the start band, timer switches T4 and T5 will be closed thereby starting the cycle of operation of the dryer. Releasing knob 64 allows it to return to the run position and timer switches T4 and T5 will open.

Referring again to FIGURE 2, note that momentary contact T4 energizes the drive motor 80. When the drive motor reaches a predetermined speed, the centrifugal switch 83 will transfer to the stationary contact 83a thereby connecting the run winding 82 to closed timer switch T2. Switch T2 will maintain the drive motor `80 running after the momentary contact switch T4 opens upon release of the twist-to-start knob 64.

The momentary contact T5 also closes to energize coil 78 and the pulser motor 71. As mentioned hereinabove, the selector knob 62 is in the ofi position therefore leaving movable contactor 72 out of engagement with fixed contactor 72a, and, therefore, the coil 78 and pulser motor 71 will be deenergized when the twist-to-knob 64 is released to again open the timer switch T5.

The electronic control circuit 67 is energized through switch T2, the centrifugal switch 83 engaging the stationary contactor 83a, the movable contactor 76 engaging the contact 761: and through the line 77. This applies alternating current to the terminal EC1 which is rectified by diode 97 to apply positive pulses of current at a rate of 60 cycles per second to the capacitor 100. Wet clothes engaging the sensor 54 within the interior of the dryer will cause the capacitor 160 to discharge through line 103, switches 92a and 92h, resistor 96 and on through the clothes. As the clothes become more dry, and the charge across the capacitor increases, to approximately 70 volts, the neon lamp 117 will ionize thereby applying a pulse of current to the gate electrode of the silicon controlled rectifier 116.

Positive anode voltage for the silicon controlled rectifier 116 is provided by the diode 106 applying pulses of halfwave current through resistor 107 to the filter circuit comprising capacitor 108 and resistor 109. Therefore, a pulse of current through neon lamp 117 to the gate electrode of silicon controlled rectifier 116 will cause the silicon controlled rectifier to be rendered conductive and it will remain conductive due to the DC potential applied at its anode. Conduction of silicon controlled rectifier 116 will energize the coil 89a. The resistor 113 connected in series with coil 89a and the silicon controlled rectifier 116 serves as a current limiting resistor to maintain the anode current of the silicon controlled rectifier within the specified limits of the device. Additionally, resistor 118 is connected in series with resistor 113 to provide a voltage divider network such that no more than 30 volts is impressed across the silicon controlled rectifier 116 during periods when the silicon controlled rectifier is nonconductive.

Energization of the coil 89a will cause the contactor 89 to close thereby energizing the timer motor 90. The timer motor will remain energized through the timer contact T2, the centrifugal switch 83 which engages the stationary contact-83a, and the contactor 89.

Energization of the timer motor 90 advances cams associated therewith to open the timer switch T3 (see FIGURE 6) to deenergize the heat source 91. However, timer contact T2 remains closed for a predetermined period of time to allow the interior of the dryer to cool down before the drive motor 80 is deenergized. Therefore, the circuit arrangement of the present invention provides the unique advantage of totally electronically controlling the drying cycle of the dryer while providing timer motor means to control such auxiliary functions as the cool down cycle.

During the cool down cycle of the control system 66, the timer motor 90 ad-vances until timer switch T2 opens, and since the antiwrinkle switch 73 is in the off position, the control ysystem 66 will be deenergized.

Now assuming that the air-heat switch is in the heat position and the antiwrinkle switch is in the on position, the following sequence of operation will occur.

When the antiwrinkle switch 73 is in the on position, movable contactor 72 engages stationary contact 72a and movable contactor 76 engages contact 76a. Therefore, upon turning the twist-to-start knob 64 to the start position, the various components of the control system 66 will be energized as mentioned hereinabove, with the addition that the relay coil 78 will be locked in the energized position through timer contact T1, its own contact 74 and the movable contact 72 engaging the stationary contact 72a. Also, the electronic cont-rol circuit 67 is energized through the timer control switch T1, contactor 74, movable contactor 76 engaging stationary contact 76a and the line 77 connected to terminal EC1.

With the heat and antiwrinkle cycles selected, the sequence of operation of control system 66 is identical to that described above until termination of the cool down cycle is reached. At this point timer switch T1 continues to energize the electronic control circuit 67 through locked in contactor 76 to 76a as well as pulser motor 71, and relay coil 78 through locked in contactor 74. The drive motor 80 may now be energized through the timer contact T1 and contactor 74 whenever the pulser switch 86 closes. The pulser switch 86, whose operation is controlled by energized pulser motor 71, is arranged to close, for example, five seconds out of every five minute interval.

Since the electronic control circuit 67 remains energized, contactor 89 will remain closed to advance the timer motor 90 during intervals when the pulser contact 86 is closed. After approximately two and one-half hours the timer 90 opens the timer contact T1 and the dry control system 66 is completely deenergized.

When the control system 66 is operated with the airheat switch 61 in the air position, the operation of the control system 66 is substantially the same as that mentioned hereinabove, the exception being that the heat source of 91 remains deenergized. With the air-heat switch in the air position, contactors 92, 92a and 92h are open thereby disconnecting the sensor 54 from the electronic control circuit 67 as well as disconnecting the wiper arm of the potentiometer 99 from the junction point 102. Therefore, the time duration of the air cycle is dependent upon the charge time of capacitor 100 in series with the full value of the potentiometer 99 together with the cool down period of the control system. The air only cycle will be followed by the anti-wrinkle cycle if the antiwrinkle switch 73 is in the on position, as shown in FIGURE 2.

Seen in FIGURE 3 is an alternate arrangement of the electronic control circuit 67 and is designated generally by reference numeral 67a. The electronic control circuit 67a utilizes the fact that timer motors operate only when full wave alternating current voltage is applied thereto, and ,remain inoperative when half-wave pulses of alternating current are applied to the motor. Therefore, the electronic control circuit 67a is modified to apply halfwave pulses to the timer motor 90 of FIGURE 2, until such time as the neon lamp 117 energizes to render the silicon controlled rectifier 116 conductive.

The electronic control circuit 67a includes a resistor 120 connected in the cathode circuit of the silicon control rectifier 116 and a resistor 121 connected to the anode of the silicon controlled rectifier 116. The other end of the resistor 121 is connected to resistor 120 at line 104.

A second silicon controlled rectifier 122 has the gate electrode thereof connected to the cathode 0f silicon controlled rectifier 116 at the junction of resistor 120. A diode 123 is connected in parallel with the silicon controlled rectifier 122 but in opposite conductive polarity with respect thereto. The anode of silicon controlled rectifier 122 together with the cathode of diode 123 are connected to a circuit point 124 which, in turn, is connected to the terminal EC3 through a line 126.

To incorporate the modified electronic control circuit 67a into the electronic control system 66, the terminal of the timer motor connected to line L2 is disconnected at the junction indicated by the reference letter A and connected to terminal EC2 as indicated by reference letter A in FIGURE 3. This modification effectively moves the electronic control circuit 67a between the timer motor 90 and line L2.

During the drying, or moisture sensing phase of the drying cycle, neither silicon controlled rectifiers 116 or 122 are conductive. When the sensor 54 senses a predetermined condition of dryness, the neon lamp 117 ionizes and causes silicon controlled rectifier 116 to become conductive. Silicon controlled rectifier 116 remains conductive due to the continuous forward bias applied thereto from the filter network comprising-capacitor 108 and resistor 109. Conduction of silicon controlled rectifier 116 causes a voltage d-rop across resistor 120. This voltage is applied to the gate electrode of silicon controlled rectifier 122 to cause conduction thereof during each positive half cycle of the alternating current voltage applied to terminal EC3. Therefore, silicon controlled rectifier 122 together with the diode 123 function together to apply full wave alternating current voltage to the timer motor 90 after the silicon controlled rectifier 116 is rendered conductive. The motor 90 will runout in the same manner as described hereinabove with reference to FIG- URE 2.

Seen in FGURE 4 is still another alternate arrangement of an electronic control circuit which can be used in the electronic control system of FIGURE 2, and is designated genrally by reference numeral 67b. The electronic control circuit 67b is somewhat simplified from that shown in FIGUR-E 3 and the unique circuit arrangenient of the components eliminates `the need of the second silicon controlled rectifier 122 of FIGURE 3.

The diode 111a has its anode electrode connected to the junction of resistor 112 and neon lamp 117 and the cathode thereof connected to a junction between a pair of resistors 130 and 131. The diode 111a operates to discharge the capacitor and neon lamp 117 whenever silicon controlled rectifier 116 is rendered conductive by providing a current path through the diode 111a and silicon controlled rectifier 116. Also connected to the junction of resistors and 131 is the cathode of a diode 132 together with one terminal of a capacitor 133. The other terminal of the capacitor 133 is connected to line 104 thereby shunting silicon controlled rectifier 116 and resistor 131. The anode of diode 132 is connected to the cathode of a diode 134 and to the line 126. The diode 134 serves the same function as diode 123, as shown in FIGURE 3.

In operation, and during the drying and sensing portion of the dryer cycle, silicon controlled rectifier 116 remains non-conductive. A direct current potential is applied to the anode of silicon controlled rectier 116 by the filter network comprising capacitor 1 08 and resistor 109. The positive potential applied to V,anode of silicon controlled rectifier 116 reverse' biases diode 132 and prevents conduction thereof. Therefore, when line L1 goes negative current will ow from terminal EC.1 through diode 134, line 126 and through the timer motor 90. However, when line L1 goes positive, current cannot fiow 9 through the diode 134 nor through the diode 132 if silicon controlled rectifier 116 is not conducting, and the timer motor 90 will not run.

Capacitor 133 is connected in parallel with silicon controlled rectifier 116 and resistor 131 to prevent line transients from exceeding the break over voltage of the silicon controlled rectiiier 116 and inadvertently causing conduction thereof.

When the sensor 54 senses the desired predetermined condition of dryness, neon lamp 117 becomes ionized thereby rendering silicon controlled rectifier 116 conductive. Therefore, when line L1 becomes positive current will now ow through L1, the timer motor 90, diode 132, resistor 131 and silicon controlled rectier 116 to line L2. As mentioned hereinabove, when line L1 is negative current flows through the timer motor 90 and through the diode 134, and the timer motor 90 will run. Diode 132 operates to prevent diode 134 from shunting silicon controlled rctier 116 during the negative half-cycle after the silicon controlled rectifier has been rendered conductive, thereby preventing silicon controlled rectifier roll 116 from shutting off until terminal EC1 is disconnected from the L1.

It should be noted that resistor 131 has a relatively small value, for example, approximately l ohms and will be negligible in series with the timer motor but will function to limit the peak currents of the silicon controlled rectier 116 when it becomes conductive to discharge capacitor 133.

A novel feature of the electronic control circuit 67b is that the junction between resistors 130 and 131 is at substantially the same potential as terminal .EC4 when the silicon controlled rectier 116 is conductive which effectively shunts charge on capacitor 100 to ground. This feature eliminates unnecessary firing of the neon lamp 117 and greatly increases the life thereof.

Seen in FIGURE is an alternate arrangement of a control system 66a. The control system 66a performs the same functions as control system 66, shown in FIGURE 2 and may utilize any of the electronic control circuits described herein.

The timer motor 90 has one terminal thereof connected to terminal EC3 of electronic control 67 and the other terminal thereof connected to an antiwrinkle switch 140 and to a line 141. The line 141 is connected to line L1 through a series of timer controlled switches T4, T1 and T2 to apply power to drive motor 80. A pulser motor 142 has one terminal thereof connected to line L2 through the door switch 70 and the other terminal thereof connected to line L1 through timer contacts T4 and T1. The pulser contact 14201 is connected at the junction between timer contact T1 and T2 and at the junction of timer contact T2 and motor 80. Therefore, closure of pulser contact 142a shunts timer contact T2 to render the motor 80 operative during the antiwrinkle cycle. A relay coil 43 has one terminal thereof connected to line L2 through door switch 70 and the other terminal thereof connected to the movable contactor of antiwrinkle switch 140. The relay contacts 143:1 of the relay 143 shunt timer contact T4, which is a momentary contactor, to lock the control system 66a in operation after the twist-to-start knob 64 has been released.

In operation, and assuming that the antiwrinkle switch 140 is in the on position, as shown on the drawing, and that the air-heat selector switch 61 is in the heat position, the control system 66a is initiated by turning the twistto-start selector 64. Turning of the twist-to-start selecor knob 64 causes the timer contacts T1, T2, T3 and T4 to close progressively as shown in FIGURE 6. However, timer contact T4 is a momentary contact and will open when the twist-to-start selector knob is released. During the short period of time that the selector knob 64 is in the start position, current ows through the momentary contact T4, timer contact T1 and the antiwrinkle switch, in the on position, to the relay coil 143. This action causes relay contactor 14311 to close and shunt momentary contactor T4 to maintain the control system 66a energized.

As the drive motor approaches the maximum speed, the centrifugal switch 83 opens thereby denergizing the start winding 81. Also centrifugal switch 93 closes to energize the heat source 91.

When the sensor 54 senses the desired predetermined condition of dryness of the clothes within the dryer the timer motor will be energized to start normal runout of timer switches T1-T3 to control the auxiliary functions of the dryer. For example, timer contact T3 opens rst to deenergize the heat source 91 while the drive motor 80 continues to run during the cool down cycle of the dryer. After aproximately iive minutes of cool down operation, the timer contact T2 opens thereby breaking energization power to the motor 80. However, electronic control circuit 67, relay 143 and pulser motor 142 will remain energized through relay contactor 143a :and the timer contact T1.

As the pulser motor 142 runs, the pulser switch 142a will be closed for approximately tive seconds during a live minute period. This action will cause the drive motor 80 to run and rotate the dryer receptacle to tumble the clothes therein. Timer motor 90 will also be energized each time pulser contact 142a closes through lines 141 and 141a. The pulser motor 142 will continue to be energized until enough time accumulates on timer motor 90 to open contact T1, which takes approximately 21/2 hours.

If the user had elected not to use the antiwrinkle cycle of the dryer, relay coil 143 is then deenergized when timer contact T2 opens after the cool down period thereby disabling all of the machine functions of the control system 66a.

Therefore, the electronic control system of the present invention provides unique and novel means for completely electronically controlling the drying cycle of the dryer while providing timer means for controlling auxiliary functions such as the cool down `and antiwrinkle cycles of the dryer.

Accordingly, it will be understood that variations `and modications may be effected without departing from the spirit and scope of the novel concepts of this invent1on.

The embodiments of the invention in which an exclu- 1sive property or privilege is claimed are defined as folows:

1. An appliance for the drying of material placed therein and for performing auxiliary functions after the material is dried comprising:

means forming a treatment zone receiving the material to be dried; ysensing means positioned within said treatment zone to sense the condition of dryness of the material;

circuit means including electronic means connected to said sensing means to produce a control signal when the material has reached a predetermined condition of dryness;

timer motor means connected to said electronic means to be energized by said control signal;

a selector switch in said circuit means;

timer means actuated by said selector switch; and

switch means operated by said timer motor means to control the timer means and the operation of the auxiliary functions of the appliance for a predetermined period of time after said control :signal is produced.

2. An appliance for the drying of material placed therein and for performing auxiliary functions after the material is dried comprising: means for receiving the material to be dried; means positioned within said means for receiving to sense the condition of dryness of the material; electronic means connected to said means for sensing to produce a control `Signal when the material has reached a predetermined condition of dryness; timer motor means connected to said electronic means to be energized by Isaid control signal; a twist-to-start switch, timer means actuated by said twist-to-start means, switch means operated by said timer motor means to control the timer means and the operation of the auxiliary functions of the appliance for a predetermined period of time after said control signal is produced, said electronic means includes selector means to preselect the predetermined condition of material dryness at which time said electronic means produces said control signal, said electronic means includes a capacitor connected to said sensing means whereby the voltage level on said capacitor is proportional to the relative dryness of the material Within said receiving means, a silicon controlled rectifier having its anode connected to a positive direct current source; a neon lamp having terminals, one of said terminals connected to said capacitor and the other of said terminals connected to the gate electrode of said silicon controlled rectifier, a diode having its anode connected at the junction of said capacitor and said neon lamp and its cathode connected to the anode of said silicon controlled rectifier, whereby, ionization of said neon lamp in response to said predetermined condition of dryness will render said silicon controlled rectifier conductive thereby producing said control signal and shunting said capacitor and said neon lamp by providing a current path through said diode and said silicon controlled rectifier, a second diode having its cathode connected to the anode of said silicon controlled rectifier, and a third diode having its anode connected to the cathode of said silicon controlled rectifier, the anode and cathode of said second and third diodes being connected together and to said timer motor, whereby, only half-wave pulses of current pass through `said timer motor due to the conduction of said third diode during the period prior to the generation of said control signal and full wave current passes through said timer motor due to the conduction of said third diode and the conduction of said second diode and said silicon controlled rectifier after said control signal is produced.

3. A control circuit for an appliance comprising: sensing means for sensing a predetermined condition of the appliance to produce a control signal in response thereto; an electronic switching device having first and second power conducting electrodes and a control electrode; a diode having anode and cathode electrodes, said anode of said diode connected to said second electrode of said switching device and said cathode of said diode connected to said first electrode of said switching device, and said control electrode connected to said sensing means to receive said control signal; an integrating means connected in series with said switching device and said diode and connected to a source of alternating current, whereby, only halfwave pulses of current pass through said integrating device due to the conduction of said diode during the period of time prior to the generation of said control signal and full Wave current passes through said integrating device and to the conduction of said diode and the conduction of said switching device after said control signal is produced, said sensing means includes a capacitor to receive a voltage charge in response to said predetermined condition, a silicon controlled rectifier having its anode connected to a source of direct current and its cathode connected to said control electrode of said electronic switching device to deliver said control signal thereto, a neon lamp having a pair of terminals, one of said terminals being connected to said capacitor and the other of said terminals connected to the gate electrode of said silicon controlled rectifier, and a discharge diode having its anode connected to the junction of said charging capacitor and said neon lamp and its cathode connected to the anode of said silicon controlled rectifier, whereby, said capacitor is maintained discharged by said discharge diode and said silicon controlled rectifier thereby preventing ionization of said neon lamp after said predetermined condition is reached.

4. A control system for an appliance to control a main function prior to controlling an auxiliary function, comprising: sensing means to sense a predetermined condition of the appliance; an electronic control circuit conected to said sensing means to produce a control signal in response to said predetermined condition; selector means in said electronic control circuit to selectively set said predetermined condition; timer means energized in response to said control signal, said timer means including a twist-to-start selector knob, first switch means to initiate energization of said electronic control circuit in response to movement of said twist-to-start knob, se'cond switch means to control operation of the auxiliary functions of the appliance in response to said control signal, and a timer motor means connected to said timer means.

5. An appliance according to claim 1 wherein said electronic means includes selector means to preselect the predetermined condition of material dryness at which time said electronic means produces said control signal.

6. An appliance according to claim 5 wherein said electronic means includes a capacitor connected to said sensing means whereby the voltage level on said capacitor is proportional to the relative dryness of the material within said receiving means, a silicon controlled rectifier having its anode connected to a positive direct current source; a neon lamp having terminals, one of said terminals connected to said capacitor and the other of said terminals connected to the gate electrode of said silicon controlled rectifier, a diode having its anode connected at the junction of said capacitor and said neon lamp and its cathode connected to the anode of said silicon controlled rectifier, whereby, ionization of said neon lamp in response to said predetermined condition of dryness will render said silicon controlled rectifier conductive thereby producing said control signal and shunting said capacitor and said neon lamp by providing a current path through said diode and said silicon controlled rectifier.

7. A control system according to claim 4 wherein said electronic control circuit includes an electronic switching device having a control electrode and first and second power electrodes, a diode having anode and cathode electrodes, said anode of said diode connected to said cathode of said switching device and said cathode of said diodel connected to said anode of said switching device, and said control electrode connected through circuit means to said sensing means to render said switching device conductive in response to said control signal, said timer means connected in series with said switching device and said diode connected to a source of alternating current voltage whereby, only half-wave pulses of current pass through said timer motor due to the conduction of said diode during the period of time prior to generations of said control signal and full wave current passes through said timer means due to the conduction of said diode and said electronic switching device after said control signal is produced.

8. A control system for an appliance according to claim 4 wherein said electronic control circuit includes a charging capacitor connected to said sensing means to receive a voltage charge in response to said predetermined condition of the appliance, a silicon controlled rectifier having its anode connected to a positive source of direct current, a neon lamp having a pair of terminals, one of said terminals being connected to said charging capacitor and the other of said terminals being connected to the gate electrode of said silicon controlled rectifier, and a discharge diode having its anode connected to the junction of said charging capacitor and said neon lamp and its cathode connected to the anode of said silicon controlled rectifier to maintain said charging capacitor discharged, thereby preventing ionization of said neon lamp after said predetermined condition is reached.

(References on following page) 13 14 References Cited OTHER REFERENCES UNITED STATES PATENTS SCR Manual (second edition), 1961. Published by 3,248,799 5/ 1966 Worst 34--45 General Electric C0., Auburn, NY., pages 34 and 36. 3,398,460 8/1968 Elders 341-45 3,402,478 9/ 1968 Hetrick 34-53 5 EDWARD G. FAVORS, Primary Examiner 

